This invention relates to a composite, structural, steel stud with a thermal break between opposite sides and with excellent acoustical properties.
The conventional residential building market has revolved around wood frame structures. Wood frame structures have dominated due to the abundance, economics and construction knowledge associated with wood and wood products. Currently, some of the dominating factors of wood frame structures are yielding to other materials. Some of these factors are pricing, quality of material, strength (hurricanes and earthquakes) and durability (termites). Today, the material cost of steel framing is comparable to that of wood. Many steel manufacturers have geared up to deal with an expanding steel frame market by installing new galvanizing plants. Markets have expanded in California""s earthquake zones since steel frame buildings can be more durable. Steel frame markets in Florida and Texas have grown to overcome termite and hurricane damage. New construction practices and construction tools have developed, as have building code standards to accept the new boom in steel frame buildings. However, a new setback has surfaced with residential steel frame building: thermal efficiency. Where high thermal efficiencies are required in the cooler climates, conventional steel frame buildings are not thermally equivalent to wood structures.
Steel studs inherently have thermal short problems. Steel studs in frames produce a thermal bridge between opposite sides of a wall frame, joist or truss member. This thermal bridging readily transfers heat across metal members, which results in excessive heating/cooling costs, condensation, and accelerated thermal rot in sheeting materials like drywall and siding. Heat transfer utilizes three basic mechanisms; conduction, radiation and convection. With typical wood framing, the wood itself is an insulator, which eliminates conduction. Effective thermal sheeting and batting insulation prevent radiation across the frame and convection within the dead space. With steel framing, the metal conducts heat across the frame. Sheeting and batting insulation reduce radiation and convection, but can not significantly reduce the thermal shorts of the steel members and their endpoint connections.
In simple words, conventional steel studs conduct cold from the outside wall to the inside wall. In severe cold climates under prolonged use, gray stripes develop on the inside wall. The stripe occurs where the conventional steel stud touches the warm inside wall. Industry has proposed several approaches to providing metal beams with a thermal break between opposite walls. No approach, however, has completely eliminated the thermal short problems associated with metal beams. Nor have these approaches provided a stud with the superior structural properties of steel and the thermal equivalence of wood.
The composite of this invention has excellent acoustical or sound dampening properties. Steel or metal studs generally are better than wood studs. The composite stud of this invention has acoustical properties better than steel or metal studs. The thermal break eliminates any direct metal connections thereby interrupting the path noise would follow.
The composite of this invention combines two metal shapes, inner and outer, with an insulating material to form a composite structural member having an insulating valve (R Value) greater than a similar steel member normally used as a stud in a residential structure. The R value of the composite member is R-2.5 to R-5 while the R value of the equivalent steel member is R-0.0098 and that of an equivalent wood member is R-2.9 to R-4.9. Thus, the composite steel member has an R value comparable to wood which is three order of magnitude better than that of a equivalent steel member. Also, the composite steel member is three orders of magnitude better than the R value of wood. The composite also has a strength comparable to that of a similar steel member normally used as a stud in a residential structure. The composite structural member eliminates any direct metal connections and thus eliminates any thermal shorts that reduce the overall insulating value (R-Value) of the composite member. The two steel shapes, inner and outer, with an insulating material form a composite structural member that has an interlocking shape which utilizes the compression strength of the insulating material and mechanically couples the inner and outer members. The interlocking shape holds the insulating material in compression and mechanically couples the inner and outer members regardless of whether the inner and outer members are in relative tension loading or compression loading. Coupling the composite structural members together forms thermally independent connections which eliminate thermal shorts between the inner and outer steel shapes. The coupling also eliminates thermal shorts between the inner and outer steel shapes and the floor and wall connections and also eliminates thermal shorts between the inner and outer steel shapes and the truss connection.
In the preferred embodiment, one shape encompasses the other shape. Preferably, an outer C shape encompasses an inner T shape. Insulation material is between the C and the T.